Work in progress centers on hormonal regulation of follicular and luteal growth and regression. Representative projects include: A single SC injection of equine anti-bovine LH results in superovulation in : cyclic and pregnant hamsters (ovulation-ca 40 eggs) and cyclic guinea pigs (ovulation of 6 eggs versus normal number of 3 3). 2. A model for inducing atresia of antral follicles has been developed. The model consists of injecting an anti-serum to PMS (an FSH-like hormone) into hypophysectomized PMS treated hamsters. Biochemical and steroid changes over a 72 h time span are being studied. 3. The ovarian interstitium of long term hypophysectomized hamsters and rats continues in vitro to produce progesterone despite lack of exposure to gonadotropins for 20-40 days. 4. The in vivo and in vitro effects of cycloheximide on ovarian steroidogenesis in proestrous hamsters are being investigated.